1. Field of the Invention
The present invention relates generally to a messaging service, and in particular, to a method and system for establishing a session for message communication between a converged Internet Protocol (IP) messaging service client and a short messaging service client.
2. Description of the Related Art
Messaging services are for providing communication between a user and a user terminal using a memory device having an accumulated transmission electronic mail box and message processing function as a type of interactive service, and includes such services as Instant Messaging (IM), Short Messaging Service (SMS), Multimedia Messaging Service (MMS) and a Push to Talk Over Cellular (PoC) service.
The IM service indicates a service of converging chatting and file transmitting/receiving functions using a specific program in an Internet environment. Recently, the development of mobile communication services allows personal mobile communication terminals, such as a cellular phone, to provide the IM service for real-time communication, which is provided by a Personal Computer (PC) via the Internet. In the PoC service, a half-duplex communication method is applied to a mobile communication service. The IM service and the PoC service are Session Initiation Protocol (SIP)-based messaging services, wherein message communication is performed by transmitting and receiving a message after establishing a session between a sending client terminal and a receiving client terminal.
For example, a process of establishing a session between two IM clients performing message communication according to the IM service will now be described. A client attempting to start message communication, i.e. an IM client A attempting to open a session, transmits an SIP INVITE message to an IM client B. The IM client B, which has received the SIP INVITE message, transmits a 200 OK message to the IM client A in response. The IM client A, which has received the 200 OK message, transmits an ACKnowledgement (ACK) message to the IM client B in response.
The SMS allows subscribers to send and receive short messages and to perform message communication without establishing a separate session. A SM client stores text input by a user in a user data portion of an SMS-SUBMIT message and transmits the SMS-SUBMIT message to an SM server. The SM server converts the SMS-SUBMIT message to an SMS-DELIVER message and transmits the SMS-DELIVER message to an SM client corresponding to a reception address. The SM client, which has received the SMS-DELIVER message, notifies of a message reception state by transmitting an SMS-DELIVERY-REPORT message to the SM server in response. Even if the SMS-SUBMIT message is converted to the SMS-DELIVER message, the text input by the user is not changed.
As described above, the messaging services use different protocols according to service types. Thus, the messaging services cannot be compatible with each other, and accordingly, a user must begin message communication only after determining whether a type of the message communication is accepted by a target client terminal. Moreover, if messaging service types supported by respective client terminals are different, it is difficult to perform message communication. For example, the IM service in which message communication begins after establishing a session cannot be compatible with the SMS in which message communication begins without establishing a session, and therefore, an IM transmitted from an IM client cannot be received by an SM client.
Thus, a new converged messaging service for converging the messaging services, such as IM, SMS, MMS and PoC services, is needed. Since a user of the converged messaging service must be able to communicate with users of the converged messaging service and users of the existing messaging services without limitation, interworking with the services such as IM, SMS, MMS and PoC must be performed. Furthermore, interworking between a messaging service in which communication is performed by establishing a session and a messaging service in which communication is performed without establishing a session must be performed.